1. Field of the Invention
The present invention relates to an information recording/reproducing apparatus suitable for recording and reading signals having a time-based continuity attribute, such as audio signals and video signals.
2. Description of the Prior Art
Information recording/reproducing apparatus using an optical disk as a recording medium can offer a high recording density more than ten times as much as that of magnetic disks by virtue of high convergency of laser beams and narrowed track pitches. With the recent progress in the field of optical disk medium techniques such as magneto-optical disks and phase-change rewritable media, rewritable media like magnetic media are being put into practical use.
With this technical progress as background, it is now on trial to add recording function to compact disks (CDs) and video disks (VDs), which have conventionally been used exclusively for reproduction or reading.
As is common knowledge, a great feature of the optical disks is that information can be recorded into and read out of the optical disks in a non-contact manner through the use of a laser beam from the optical head.
More specifically, in the conventional information recording/reproducing apparatus incorporating an optical disk, a laser beam emitted from the optical head which is approximately 1 mm apart from the surface of the optical disk is applied to tracks formed at a pitch of approximate 1.6 .mu.m through a transparent substrate material having a thickness of 1.2 mm, and the laser beam is modulated at a recording power level by a recording signal as focusing and tracking of the laser beam is performed, so that data is recorded. Reproduction of data, on the other hand, is carried out by applying a subdued laser beam to the optical disk and demodulating a signal obtained from reflection light of the laser beam.
However, as described above, the optical head is in non-contact with the optical disk, the track pitch is as narrow as 1.6 .mu.m or so, and the laser beam has no inertia. As a result, the conventional information recording/reproducing apparatus are liable to cause track jumps of the optical head due to external shocks or vibrations, thus having difficulty in recording audio signals and video signals having a time-based continuity attribute.
Another apparatus is known which is adapted to detect a track jump of a head and halt a recording operation (Japanese Laid-open Patent Application No. 57-150144 issued in 1982).
This apparatus, however, merely halts a recording operation upon detection of a track jump, and does not perform further data recording. Therefore, this apparatus is not suitable for recording audio signals and video signals having a time-based continuity attribute.